How to understand tyre wall information

In this video tutorial, we met up with an expert from the Institute of Advanced Motorists to explain all those mystifying numbers on the side of your car tyres, and why it's important to get them right when replacing them...

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James Baggott: Ok, I’m here with Tim Shallcross from the institute of Advanced motorists, who’s going to help us understand those strange letters and numbers that are on the side of a tyre. So, Tim can you explain to me the most important ones that are on here?

Tim Shallcross: Well, first of all, you want the right size of tyre, so if we get down here and have a look, this is it, when your ringing round to find the tyre price that’s the one they’ll ask you, 235/60 that’s the width of the tyre and how deep it is basically we won’t go into it too much. And this number 18 is the size of the wheel, so, the full diameter of the wheel.

JB: So the ‘R’ is always the same?

TS: What it says basically means is "radial". Then you need to go into these other numbers and these are actually much more important, you’re always going to get that one right, but you need to specify that it’s a 103V in this case.

The 103, is the load rating at the time, especially a car like this, it’s pretty heavy, you need to get one that’s capable of supporting that load. So that is an important number.

V is the speed rating, that’s not because you might think I’m only going to do 70 miles an hour on the motorway, it’s the speed it’s capable of breaking safely from.

Its handling that acceleration, handling that breaking, that’s why the speed rating of the tyre is also critical.

JB: Is that always going, is that going to be different on other cars, I mean?

TS: Yes, it will be, more powerful cars have higher speed ratings it’s as simple as that. So you get speed ratings as low as, H for example.

They're all in a code, you can Google them and they’ll tell you exactly what they are, same as the load rating, that doesn’t relate to anything, other than you look it up on a table and it says it’s so many kilos.

All these things are coded, but they're not straightforward so if you need to know what it is by all means look it up. But, the key thing is you get something that’s 103 and V for the speed rating. Then you’ll have the tyre that’s capable of supporting this vehicle and taking the power that it produces.